1. Field of the Invention
The present invention relates to the field of electronic components, and in particular to a method and apparatus for hot-pluggable electronic component connection.
2. Background Art
In some electronic systems, it is desirable to connect and disconnect components (e.g., an optical transceiver) without turning off the electronic system. An electronic component which can be connected to an electronic system without turning off the electronic system is termed xe2x80x9chot-pluggablexe2x80x9d or xe2x80x9chot-swappable.xe2x80x9d Hot-pluggable components have multiple connection lines which connect to the electronic system. These lines must be connected and disconnected in a specific order. Additionally, hot-pluggable devices must be accessible only from the front for maintenance and reconfiguration. Thus, it should be easy for a human to remove a hot-pluggable device. In prior art methods, connection lines are all on the same side of a component. These methods are expensive, inefficient and not easily accessible. These problems can be better understood by a review of hot-pluggable components.
Front Hot-Pluggable Components
During insertion of a hot-pluggable device, the circuits of the device are protected by a protection scheme. Some prior protection schemes have severe limitations for high performance devices which make reliable, robust operation difficult or costly to achieve. A level of protection may be designed into the device""s input/output signal lines to protect against the effects of the electric transients that occur during insertion of a hot-pluggable device.
Protection is more complicated when a device contains internal data storage such as internal registers (e.g., implemented by Random Access Memory, RAM, with device internal battery backup), particularly when the data is essential to the function of the device. During device initialization (start-up) operation or during a controlled shutdown, an uncontrolled hot-insertion or hot-removal might change the data in the data storage. When the accidentally and randomly changed data is interpreted by the device at a later time, a malfunction or erroneous behavior occurs. However, robustness is improved by using a mechanical line connection sequencing.
Hot-pluggable components have three types of connection lines: a ground line, power lines, and signal lines. When a hot-pluggable component is connected to a system, the ground line must connect to the system first followed by the power lines. After the ground and power lines are connected to the system, the signal lines are connected to the system. The component is, then, recognized by the system and initializes itself properly.
FIG. 1 illustrates the process of connecting a hot-pluggable component to a system. At step 100, the ground line is connected to the system. At step 110, the power lines are connected to the system. At step 120, the signal lines are connected to the system.
When disconnecting a hot-pluggable component, the lines are disconnected in the reverse order they were connected. First, the signal lines disconnect, followed by the power lines. Finally, the ground line disconnects and disconnection is complete. The order of line connection and disconnection is an important factor in ensuring that the component and electronic system are not damaged by connecting or disconnecting hot-pluggable components without turning the system off.
FIG. 2 illustrates the process of disconnecting a hot-pluggable component from a system. At step 200, the signal lines are disconnected from the system. At step 210, the power lines are disconnected from the system. At step 220, the ground line is disconnected from the system.
FIG. 3 illustrates a prior art hot-pluggable component. The component (300) has connection pins for the ground line (310), the power lines (320) and the signal lines (330). Theses connection pins are inserted into a system connector (340) typically attached to a printed circuit board (PCB) (350) already coupled to the system such that a line is connected to the system when its connection pin contacts the system connector.
The connection pin for the ground line is longer than any other pin. Thus, the ground line will connect before all other lines during connection. Likewise, the ground line will disconnect before all other lines during disconnection. Similarly, the connection pins for the power lines are longer than the connection pins for the signal lines. Thus, the power lines will connect before the signal lines during connection and disconnect before the signal lines during disconnection.
However, when the component is connected by moving the component in a direction parallel with the surface of the PCB connecting the connector to the system, a strong mechanical sheer force parallel with the surface of the PCB is applied on the soldering between the system connector and the PCB. Thus, repeated connections and disconnections could cause the system connector to disconnect from the PCB. Additionally, space on such connectors is limited. Thus, increasing the amount of signal lines requires that the area of the connection for each line be reduced. Reducing the area for each connector reduces the entire connector""s fault tolerance level since all connections must line up more precisely.
In some prior art methods, high performance single and multiple electrical connectors are placed at the rear side or on the bottom of the hot-pluggable device. By increasing the width of the connector, room is made available for more electrical lines. Use of arrays also allow more signal lines to be used. However, a wide, multiple line connector poses several problems. Industry equipment practice minimizes the width and height of hot-pluggable devices. The addition of multiple parallel lines to the connector to accommodate higher device frequency requirements unacceptably increases the height or width of the hot-pluggable device. Thus, the scalability of prior art methods for increased number of multiple lines is limited. The mating part of the connector on the circuit board causes a long signal path inside the connector where high frequency impedance matching is needed. The high frequency impedance matching typically results in a bulky and expensive connector and signal degradation. Additionally, since the signal leaves and enters the device at the opposite ends of the optics in the device, the signal path cannot be optimized.
FIG. 4 illustrates an additional problem with prior art methods. The component (400) is positioned parallel to the PCB (410) of the system and the signal lines (420) of the component are attached to the connector (430) of the PCB. However, a gap (440) exists between the PCB and the component. The signal traveling between the system and the component must traverse this gap. A larger gap results in an increase in the amount of time required to propagate a signal and a degradation of the signal. Thus, large gaps reduce the component""s efficiency. Additionally, it is necessary to shield the lines carrying the signal through the gap to reduce error caused by electromagnetic interference. The shielding increases the size and cost of the connector.
The present invention provides a method and apparatus for hot-pluggable electronic component connection. In one embodiment of the present invention, ground and power line couplings with a system are formed by moving the component in one direction while signal line couplings with the system are formed by moving the component in another direction.
In one embodiment, a guide rail system causes a hot-pluggable component to move in a direction which couples, first, the ground line and, then, the power lines to the system. After the ground and power lines are connected, the guide rail system causes the hot-pluggable component to move in another direction which couples the signal lines to the system. In another embodiment, a latching mechanism holds the component in place once the signal lines are coupled to the system. In this embodiment, an ejection system releases the latching mechanism and allows removal of the component.
In one embodiment of the present invention, signal lines are coupled to the system in the same plane as a PCB. In this embodiment, the area used for signal line couplings is increased when more signal lines are present. This increases scalability in two dimensions for the addition of signal lines. Thus, signal lines are added without sacrificing industry practice space requirements of the component or decreasing the fault tolerance of signal line couplings. In one embodiment of the present invention, the front hot-pluggable component is an optical transceiver.
In one embodiment, connections are made using a conductive interposer. The interposer (e.g., anisotropic conductive elastomer) minimizes the signal path. In one embodiment, a ground pattern is etched into the component and the PCB circumscribing the signal line connections. This embodiment minimizes electromagnetic interference without increasing the dimensions of the component or the connector.